A good start would be a strike system for abuser accounts, after the 3rd strike you get put into the global blacklist that should eventually exist for all bots.

There's also need to be some community consensus on what abusing is, using bots on the 6th day of the post is obviously abuse and just reward pool raping but to what extend is using bots to promote your post also abuse? maybe a cap can be set in how much sbds/steem a user can give to bots for a certain post (i'm aware this can be hard to implement and there will always be non-compliant bots) and of course, community consensus should be reached for this cap, maybe a cap of 25/50 sbd/steem per post can be set or any other value really, just to stop seeing those post in trending with 500$+ of bot votes.

Just throwing my 1c into the convo after all i'm only a minnow lol.